1. Field of the Invention
The present invention relates to an electronic azimuth meter (hereinafter, referred to also as xe2x80x9celectronic compassxe2x80x9d) having a magnetic detector including a magnetic sensor, further particularly to a method of adjusting (hereinafter, referred to also as xe2x80x9ccalibrationxe2x80x9d or xe2x80x9ccorrectionxe2x80x9d) of an electronic azimuth meter and an apparatus used for carrying out the method.
2. Description of the Prior Art
According to a magnetic detector comprising a magnetic sensor (typically comprising a bridge circuit of an MR element) and an A/D converter, sensitivity (span of output) and offset of the detector differs for each detector and therefore, it is necessary to individually adjust an electronic azimuth meter having the magnetic detector under a magnetic field produced by a magnetic field generating apparatus.
In adjusting thereof, in order to synchronize the magnetic field generating apparatus with the magnetic detector of the electronic azimuth meter, a control unit of the magnetic field generating apparatus is electrically connected to the electronic azimuth meter by a wiring and a case back or a battery of the electronic azimuth meter is detached for the electric connection.
However, according to the electronic azimuth meter, there is a concern of changing an effective magnetic field applied to the magnetic sensor of the electronic azimuth meter by presence or absence of a battery or the case back and there is a concern that it is difficult to properly adjust the electronic azimuth meter.
The invention has been carried out in view of the above-described point and it is an object thereof to provide an adjusting method of an electronic azimuth meter capable of properly adjusting the electronic azimuth meter and an apparatus used for carrying out the method, that is, an electronic azimuth meter adjusting system, a magnetic field generating apparatus for the adjusting system and an electronic azimuth meter adjusted by the adjusting method.
In order to achieve the object, according to an aspect of the invention, there is provided a method of adjusting an electronic azimuth meter which is a method of adjusting an electronic azimuth meter having a magnetic detector, the method comprising the steps of generating magnetic fields including a magnetic field for starting to adjust the electronic azimuth meter at magnetic field generating means capable of generating a magnetic field stronger than the geomagnetism by an adjusting magnetic field generating sequence, arranging the electronic azimuth meter for acquiring output data of magnetic sensors by a data acquisition sequence for adjusting the electronic azimuth meter in correspondence with the magnetic field generating sequence in a magnetic field region produced by the magnetic field generating means by the magnetic field generating sequence, and starting the adjusting data acquisition sequence of the electronic azimuth meter by sensing the strong magnetic field for starting to adjust the electronic azimuth meter by the magnetic detector.
According to the method of adjusting an electronic azimuth meter of the invention, since xe2x80x9cthe strong magnetic field for starting to adjust the electronic azimuth meter is generated by the magnetic field generating means and the sequence of acquiring data for adjusting the electronic azimuth meter is started by the strong magnetic field for starting to adjust the electronic azimuth meterxe2x80x9d, by only generating the strong magnetic field for starting to adjust the electronic azimuth meter by the magnetic field generating means, the sequence of acquiring data for adjusting the electronic azimuth meter can be started. Further, according to the method of adjusting an electronic azimuth meter of the invention, since xe2x80x9cthe magnetic field generating means generates the magnetic field by the sequence of generating the magnetic field for adjusting the electronic azimuth meter and the electronic azimuth meter for acquiring output data of the magnetic detector by the sequence of acquiring data for adjusting the electronic azimuth meter in correspondence with the sequence of generating the magnetic field, is arranged in the magnetic field region produced by the magnetic field generating means by the magnetic field generating sequencexe2x80x9d, after starting the adjusting data acquisition sequence of the electronic azimuth meter, the electronic azimuth meter can acquire, as adjusting data, output data of the magnetic detector by the adjusting data acquisition sequence in correspondence with the magnetic field generating sequence under the magnetic field produced by the adjusting magnetic field generating sequence by the magnetic field generating means. That is, the magnetic field generating means generates the magnetic field for adjustment by itself by the adjusting magnetic field generating sequence and the electronic azimuth meter acquires output data (data for adjustment) of the magnetic detector by itself by the adjusting data acquiring sequence. The adjusting data acquiring sequence is previously adjusted to progress in correspondence with the adjusting magnetic field generating sequence and the two sequences are started actually simultaneously by generating the magnetic field for starting the adjustment and detecting the subject magnetic field. Therefore, even when a control unit of the magnetic field generating means and the electronic azimuth meter are not electrically connected by a wiring, the two sequences can be progressed at actually the same or corresponding timing with the magnetic field as a medium. As a result, the electronic azimuth meter can be adjusted by progressing the two sequences actually similar to the case of adjusting the electronic azimuth meter by exchanging synchronizing signals between the control unit of the magnetic field generating means and the electronic azimuth meter. Further, electric wiring connection is dispensed with between the control unit of the magnetic field generating means and the electronic azimuth meter and therefore, it is not necessary to detach a battery or a case back in the adjustment, the electronic azimuth meter can be adjusted while maintaining the electronic azimuth meter in a mode of a finished product actually used and therefore, the electronic azimuth meter can properly be adjusted by avoiding a concern of causing error derived from presence or absence of the battery or the case back in the adjustment.
In the specification, a technical term of xe2x80x9cmagnetic fieldxe2x80x9d is used to define xe2x80x9cmagnetic flux densityxe2x80x9d unless specified otherwise and a case of designating inherently xe2x80x9cmagnetic flux densityxe2x80x9d is referred to as xe2x80x9cmagnetic fieldxe2x80x9d. In designation thereof, not H but B is used. Further, in the specification, strong magnetic field signifies a magnetic field stronger than a magnetic field by the geomagnetism (about several xcexcT (micro tesla) and xe2x80x9cstrongxe2x80x9d designates a magnetic field which can be differentiated from the magnetic field by the geomagnetism owing to the intensity of the magnetic field. Therefore, for example, the strong magnetic field designates a magnetic field several times as much as or more than the geomagnetism, preferably, about ten times or more thereof, typically about 100 xcexcT. Naturally, further stronger magnetic field may be used, however, in order to minimize a concern of strongly magnetizing a magnetic part of an electronic azimuth meter, it is preferable that the magnetic field is not strong excessively. Further, in the specification, unless specified otherwise, azimuth or azimuth angle is represented by notation xcfx86, north is represented by 0 degree, east is represented by 90 degree, south is represented by 180 degree and west is represented by 270 degree. The geographical azimuth angle is represented by notation xcex8 and is described as display azimuth angle. Further, xcfx86+xcex8=360xc2x0.
The adjusting magnetic field generating sequence typically includes four azimuth magnetic fields generating steps for successively generating magnetic fields of four azimuths. By measuring the output of the magnetic detector under the magnetic fields of the four azimuths, there can be carried out calibration of the electronic azimuth meter for providing a predetermined output by correcting influence by a magnetic part included in the electronic azimuth meter. However, so far as such a calibration of the electronic azimuth meter is possible, in place of the magnetic fields of the four azimuths, other set of magnetic fields may be generated.
Further, the adjusting magnetic field generating sequence typically includes a span (sensitivity) and offset adjusting magnetic field generating step for adjusting span (sensitivity) and offset of an output of the magnetic detector of the electronic azimuth meter and the span and offset adjusting magnetic field generating step typically comprises a span and offset adjusting magnetic field generating step of an output of an A/D converter connected to magnetic sensors of the magnetic detector and constituting a portion of the magnetic detector.
The magnetic detector of the electronic azimuth meter typically includes a magnetic sensor such as an MR element (transducer for converting a magnetic field signal into an electric signal) and an A/D converter for converting an analog output (data) of the magnetic sensor into digital data. Therefore, the offset and the sensitivity (span) of the magnetic detector are dependent upon the characteristic of the magnetic sensor main body or a related element of the sensor (current for driving an element of the sensor) and the characteristic of the A/D converter. However, so far as the respective element of the magnetic detector is maintained in a predetermined range, by adjusting sensitivity of the A/D converter (span of an output of the A/D converter) and offset of an output of the A/D converter providing final output of a total of the magnetic sensor, that is, the total of a magnetic field detecting system, the span and the offset of the magnetic detector, that is, the magnetic field detecting system can be adjusted.
Further, in order to achieve the above-described object, according to another aspect of the invention, there is provided a system of adjusting an electronic azimuth meter, the system comprising a magnetic field generating apparatus capable of generating a magnetic field stronger than the geomagnetism for generating a magnetic field including the strong magnetic field for starting to adjust the electronic azimuth meter, and an electronic azimuth meter including a magnetic detector for acquiring output data of the magnetic detector by a data acquisition sequence for adjusting the electronic azimuth meter in correspondence with the magnetic field generating sequence, the electronic azimuth meter comprising an adjusting data acquisition sequence starting control unit for starting the data acquisition sequence for adjusting the electronic azimuth meter when the magnetic detector arranged below a magnetic field produced by the magnetic field generating means by the magnetic field generating sequence, senses the strong magnetic field for starting to adjust the electronic azimuth meter.
Further, according to another aspect of the invention, there is provided a magnetic field generating apparatus which is a magnetic field generating apparatus for a system of adjusting an electronic azimuth meter capable of generating a magnetic field stronger than the geomagnetism, wherein a magnetic field including the strong magnetic field for starting to adjust the electronic azimuth meter for starting to acquire output data of a magnetic detector by an adjusting data acquisition sequence at the electronic azimuth meter by an adjusting magnetic field generating sequence.
Further, according to another aspect of the invention, there is provided an electronic azimuth meter which is an electronic azimuth meter having a magnetic detector for acquiring output data of the magnetic detector by a sequence of acquiring data for adjusting the electronic azimuth meter in correspondence with a sequence of generating a magnetic field for adjusting the electronic azimuth meter of a magnetic field produced by a magnetic field generating apparatus, the electronic azimuth meter comprising a control unit of starting the sequence of acquiring data for adjusting the electronic azimuth meter for starting the sequence of acquiring data for adjusting the electronic azimuth meter when a strong magnetic field for starting to adjust the electronic azimuth meter representing start of the sequence of generating the magnetic field for adjusting the electronic azimuth meter is detected by the magnetic detector.
The electronic azimuth meter may be of a mode of, for example, an electronic timepiece having an electronic azimuth meter integrated to the electronic timepiece. In that case, the electronic timepiece having the electronic azimuth meter is constituted to be switchable between a time piece mode operated as an ordinary electronic timepiece and an azimuth meter mode operated as an electronic azimuth meter by a push button switch for switching the modes.